1. Field of the Invention
The present invention relates to a method and apparatus for producing plastics moldings made of laminations of different plastics for such applications as door linings in automobiles.
2. Description of the Prior Art
Plastics are employed extensively for the type of moldings that are used for the interior trim in automobiles. Such members are fabricated by using a suitable method to mold a lamination of different plastics. Melt stamping is one such forming method that is being used in the prior art. One example of this process that can be cited is that disclosed by Japanese Laid-open Patent Application 62-181111. As disclosed, the fabrication comprises of placing a skin material in a mold made of a mold plunger and a mold cavity and charging a molten resin thereonto, then closing the mold to apply pressure and cooling to form a laminate of plastics moldings. In charging or loading the molten resin, a jet nozzle was provided which could be moved as required by a motor downstream of the extruder, to jet in a staggered or zigzag line in accordance with the intended shape into which the resin was to be molded. Details of the injection orbits or paths are described in Japanese Patent Publication 59-17931. This method is generally referred to as flow molding.
However, because the prior art as described above moves the jet nozzle so that it follows a predetermined orbit or path while performing the injection, it has the drawback of requiring considerable time for the completion of the injection, 12 seconds, for example, thus extending the operation time. In addition, because of the length of the injection time, there is a difference in the temperature of the resin of around 30.degree. C. between the start of the jetting and the temperature at the completion of the jetting. Applying pressure in this state is undesirable because of the adverse effects on the quality of the product, in the form of flow marks and weld marks and the like. Furthermore, even if an injection orbit suitable for the shape of the finished product is used, it has been impossible to avoid deflection in the specified orientation characteristics corresponding to the injection orientation.
Because, as mentioned above, there is non-uniformity in temperature between the beginning and the end of the injection, the extrusion temperature has had to be increased in order to ensure the requisite temperature in molding. This also results in a higher injection temperature, and when the molten base resin is charged onto skin material made of a foam, a protective barrier sheet has been necessary.